Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates

A₂B₂O₇ oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho₂Zr₂O₇ and praseodymium zirconate Pr₂Zr₂O₇ via Polymerized-Complex Method (PCM). Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C) fine-crystalline, single-phase material is obtained. Thermal diffusivity was measured in temperature range 25-200°C, Ho₂Zr₂O₇ exhibits lower thermal diffusivity than Pr₂Zr₂O7. Additionally, PrHoZr₂O₇ was synthesized. The powder in as-calcined condition is single-phase, but during the sintering decomposition of solid solution took place and Ho-rich phase precipitated. This material exhibited the best insulating properties among the tested ones.